But now we have a Google AdWords Help thread with confirmation from a Googler about at least one or two keywords being reported inaccurately.

The advertiser said:

I have done a checking in two different period of times - one today and one about a month ago.
I am getting now completely different results from what I got a month ago:
Market - Germany, Language - German

I realize there can be changes in the numbers, but this is too radical to make sense.

Google Keyword Tool Engineer, Scott, said:

Thank you for the heads up on this issue. I'm seeing the same thing internally for those particular keywords and have passed on the details to the rest of the dev team. I'll post back here once we find out more.

So Google is now admitting to an issue so maybe other issues will be found when they debug this?